package jucPC;

import jdk.nashorn.internal.ir.CallNode;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 线程之间的通信问题：生产者和消费者问题
 * 线程交替执行 A B操作同一个变量 num=0
 * A num+1
 * B num-1
 */
public class ConsumeAndProduct {
    public static void main(String[] args) {
        Data2 data = new Data2();

        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        },"A").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        },"B").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        },"C").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        },"D").start();


    }
}
//判断等待，业务，通知
class Data2 {//数字，资源类
    private int num = 0;
//只要是并发编程一定会有锁。

    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();
//condition.await();//等待
//condition.signalAll();//唤醒全部

    // +1
    public  void increment() throws InterruptedException {
        lock.lock();
        try {

//            业务代码
            // 判断等待
            while (num != 0) {
                condition.await();
            }
            num++;
            System.out.println(Thread.currentThread().getName() + "=>" + num);
            // 通知其他线程 +1 执行完毕
            condition.signalAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    // -1
    public  void decrement() throws InterruptedException {
        lock.lock();
        try {
//            业务代码
            // 判断等待
            while (num == 0) {
                condition.await();
            }
            num--;
            System.out.println(Thread.currentThread().getName() + "=>" + num);
            // 通知其他线程 -1 执行完毕
            condition.signalAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }



    }
}
/*
执行结果：
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
 */